Windowsill Repair

Our south-facing windowsills are exposed to our worst weather, and
they're showing signs of damage. How should I repair them?

—Bob Welsh, Duluth, GA.

A:

Tom Silva replies: For this kind of wood repair, you can't beat the high bonding strength of a two-part, wood-compatible epoxy adhesive. But don't just slather the stuff on and expect your problem to be solved. You have to prep the wood thoroughly by removing any paint or decayed wood so that the epoxy has something solid to bond with.

For the past decade or so, I've been working with an epoxy made by Advanced Repair Technology that is formulated to expand and contract with wood. To ensure good adhesion, it's applied in two steps: primer, then filler.

After prepping and sanding the wood, mix up and brush on the thin epoxy primer, which penetrates the wood fibers. Wait 10 minutes, then mix the epoxy filler and trowel it over the damaged areas with a putty knife. When the filler cures, sand it smooth. The filler is so thick that one coat is generally sufficient, but two may be required for very large repairs. Just make sure to sand before putting on a second coat or painting it.